1. Field of the Invention
Reinforced concrete construction frequently utilizes reinforcing bars suspended within the concrete. Often these bars are suspended on chairs at specified heights. The present invention relates generally to a chair for suspending bars within reinforced concrete. The chair can be used to support reinforcing bars as well as other long bodies, such as pipes, ducting or conduit.
2. Description of the Prior Art
Reinforced concrete construction has been around for many years. Reinforcing bars are embedded in the concrete to improve the strength of the final concrete. Concrete has a very high compressive strength, but the tensile strength is improved significantly by utilizing reinforcing bars within the concrete. These reinforcing bars are typically suspended at a specified height which varies from one job to the next depending on the concrete specifications for each job. In the past, metal chairs have been used to support the bars; however metal chairs have many disadvantages. Metal at the bottom of the chair is exposed and provides an initiation point for rust. This rusting causes the chairs to expand because the metal oxide takes up a larger volume than the metal. As the rusting chair expands, the concrete cracks and the concrete structure is weakened.
There are many chair designs in existence today. For example, Liuzza, in U.S. Pat. No. 4,060,954, discloses a base plate with lugs for receiving the legs of a chair. The height of the support is varied by stacking one chair on another. In a stack of these chairs, bars can be supported on each chair so that bars can be simultaneously supported at several different elevations within the stack of chairs.
Vigh, in. U.S. Pat. No. 4,080,770, discloses a plastic base and a metal wire spacer. The metal wire spacer is received in the plastic base. The plastic base may have tabs which can be used to secure the base to a substructure. The bars are supported at different heights by inserting different size wire spacers into the plastic base.
U.S. Pat. No. 4,835,933 by Yung discloses a support that has a base and a central vertical post that ends in a saddle, wherein the saddle is adapted for receiving a bar. A separate clamp member has arms and is received in holes in the saddle, wherein these holes are beside the central post. The arms of the clamp member hold the first bar and hooks in the clamp member hold the second bar transverse to the first bar. Different size supports are used to hold bars at different heights, and small adjustments can be made by placing an extender on top of the saddle portion of the support.
Lowery, in U.S. Pat. No. 5,595,039, discloses another chair. This chair has a base and a cap which are connected by a stem. The stem can be rebar, which is available at most job sites. The cap has a slot for holding the reinforcing bar and the height of the support can be adjusted by cutting the stem to the desired size. Thus, the stem can be cut at the job site to position the bar at the correct height.
Verelli et al., in U.S. Pat. No. 6,354,054, discloses a rebar chair with a body and four legs below the body. Two transverse bars are received between the four legs and are wired to the body or are supported on another chair of a different design placed between the legs. At least a third bar can be received in a saddle on top of the body.
U.S. Patent Published Application Number 2004/0261352 A1 by Bennett et al. discloses a support chair with a tapered body and a plurality of legs. The body is generally tapered so that the legs get further apart as they get lower, and there are notches on top of the body to hold transverse bars. The body is designed so additional chairs can be stacked on top of the supporting chair to adjust the height at which the bars are supported.
Screed supports are also used in concrete construction to level a concrete slab. Pilj, in U.S. Pat. No. 1,852,673 discloses a screed support which has a post and a separate support section. The post is driven into an underlying base, and the support section is attached to the post. The height of the support is adjusted by attaching the support at different positions on the post. The support is adapted to receive a leveling device for leveling the concrete.
Another screed support is disclosed by Cox in U.S. Pat. No. 2,551,826. Cox describes a post with a bottom portion which is adapted to be attached to an underlying base. The bottom of this post is pointed and threaded so that it can be screwed into the underlying base. A separate saddle has a sleeve which is slid over the top of the post. The height of the saddle is determined by sliding a nail through nail holes in the sleeve wherein the nail is engaged in notches in the post. The saddle is adapted to receive a leveling device.
Hillberg, in U.S. Pat. No. 3,006,115, describes another screed support. This screed support also has two parts. The first is a base which supports a socket and the second part is a cradle. The cradle has a threaded shank with an adjusting nut. The shank fits into the socket and the height of the cradle is set by the adjusting nut which abuts the socket. The cradle is adapted to receive a straight edge or a bar for leveling the concrete.